Help with picture and frame: sending to England

[beagledave]

I have a FB friend who lives in London (I'm in Iowa). She did a favor for me and I'd like to send her a token of thanks. She enjoys some photographs that I've take on butterflies in my garden, so a friend suggested a print of that. What kind of frame (I'm still not sure of size yet) would be lightweight enough and sturdy to survive shipping to the UK. Are there rubber/plastic frames that would work for that sort of thing?